It's no easy business, regulating pollution-prone industries, especially at a time when technology is changing and in a place where everyone wants jobs.

The latest case involves Shenango Inc. on Neville Island. It runs a coke plant that is a fairly regular polluter, having violated smoke limits on 310 days in 1998 and 327 days in 1997. Now Shenango and Antaeus Energy, a company it will merge with next month, are seeking a permit to build a new coke plant next to the old one. The Allegheny County Health Department, which enforces federal clean air laws locally, says it will probably recommend that the permit be issued.

Why would that be? The company already has trouble meeting federal limits with a plant that makes 360,000 tons of coke a year. Should that kind of performance be rewarded with a license to produce 500,000 tons?

Shenango's residential neighbors, downwind and across the Ohio River, have a right to wonder.

More than two dozen people protested the situation last Tuesday before a meeting of the health department's air pollution control advisory committee. To them, a manufacturer with a six-year record of violations should have to prove itself before winning permission to move on to bigger and better things.

If only it were that simple.

While it's impossible to defend Shenango's record of violations and fines (which have exceeded a quarter million dollars), those who want clean air along the Ohio should be encouraged by the potential that lies ahead.

This is not the same old company patching and repairing the same old coke plant. This is Shenango heading into a business union with Antaeus, a firm with greater financial resources and a better track record on clean air.

To be ready for that day, the companies are installing a plant that is eventually likely to replace the current coke works.

The new plant, with up-to-date technology, will be more friendly to the environment than its predecessor. Moreover, as a condition of getting a permit to build the facility, Antaeus will have to satisfy the health department's demands that it bring the old coke battery, which will continue to operate, into compliance.

The company's degree of success there will be known sooner rather than later, since the compliance deadline is June 30. So far this year, Shenango has improved its desulfurization capability and reduced its total violation time.

While Antaeus may have a permit by the end of June to begin building the new facility, construction won't be finished for 18 months. Besides, the company can't open the plant without an operating permit, which Antaeus would have to seek later from the health department. That's a lot of leverage for county regulators.

In addition to cleaner air, the new plant will bring 50 jobs, on top of the 200 that exist at the old facility. This overall package of improvements - a better-run old plant, a superior new plant and additional employment - is worth seeking, but only if the county health department is vigilant about Shenango-Antaeus holding up its end of the bargain.